Sander head



Patented Feb. 10, 1953 SANDER HEAD George W. Bruner,

Indianapolis, Ind.

Indianapolis, Ind., assignor,

by mesne assignments, to Anton Vonnegut,

Application May 26, 1951, Serial No. 228,453 Claims. (Cl. 51-191) This invention relates to a sander head, particularly of the expanding self-adjusting type wherein there is provided a plurality of radiallymovable segments acting under centrifugal force to tighten against the abrasive belt and permit of a cushioning effect when engaging with the work.

In sander heads of this type it has been customary to provide a circular abrasive belt passing directly around the head with which the segments engage. Upon rotation of the head, centrifugal force causes the segments to firmly engage the belt in theii` expanded position so that there will be no slippage therebetween. With the circular belt structure the abrasive becomes worn, overheated and destroyed in a short time, requiring replacement at frequent intervals.

It is the purpose of this invention to provide a structure of the above character, but wherein the overall length of the abrasive belt may be greatly increased to provide a substantially greater length of abrasive surface and thereby increase the life of the belt. By this arrangement both the life and usefulness of the belt may be increased, and where desired the diameter of the head may be decreased for permitting application thereof to interior surfaces.

A feature of the invention resides in the structure of the head in association with an internally looped belt so arranged with respect to the radially movable segments as to increase the length of the belt and cause a creeping action of the belt over the respective segments during use. Such creeping action continuously feeds the belt over the segments in such manner as to present fresh relatively cool abrasive surfaces about the head as theexposed and heated surfaces become worn.

Other features and advantages of the invention will become more readily apparent from the following specifications and the attached drawings.

The full nature of the invention will be understood from the accompanying drawings and the following description and claims:

Fig. 1 is a side elevation of one form of abrasive head with a portion broken away and the upper half thereof shown in central vertical section.

Fig. 2 is a section taken on the line 2-2 of Fig. 1.

Fig. 3 is a side elevation showing a modified form of head with the upper portion thereof shown in central vertical section.

Fig. 4 is a section taken on the line 4-4 of Fig. 3.

In the drawings there is shown a sander head as illustrative of one modification of the inven- 2 s tion, which head comprises a pair of annular opposed side plates I0 and Il secured to the hub I2. Said hub is provided on one end thereof with a retaining and driving flange I3 secured to the plate I@ by the screws I4. Mounted adjacent the periphery of the plates I0 and II and extending therebetween there is an annular series of spaced pairs of guide pins I5 and IB- arranged in annularly spaced relation about the periphery of said plates. The pins of each pair are in radially spaced alignment with each other. Said pins are rigidly and permanently secured at one end to the plate It and are provided with reduced ends adapted to be received in suitable bearing recesses provided in the plate I I.

Slidably carried by each pair of said pins I5 and I6 there is an applicator pad I'I forming a segment of the head. Each oi' said segments may preferably comprise a metal base plate I8 carrying a looped strap I9 extending inwardly therefrom and embracing a pair of pins I5, I6. The looped strap is elongated to extend radially inwardly and of greater overall length than the overall distance between the pins so as to freely slide thereon from a normally restricted position, as shown in Fig. 1, to an extended position under the influence of centrifugal force upon rotation of the head.

Also engaged and secured between the two side plates adjacent the hub I2 there is .an annular series of circumicrentially spaced bearing pins located radially inwardly from the space between the respective applicator pads. Said bearing pins mount a cylindrical roller 2l for free rotation thereabout. Each of the bearing pins has one end thereof rigidly secured to the plate I0, the other end being slidably receivable in a recess provided in the plate I l. The plate I I is movable from the guide pins and bearing pins to permit of convenient mounting of -the applicator pad segments Il, and the abrasive belt to be hereinafter described. Such plate II is locked in place by a suitable lock nut 22 threaded on the adjacent reduced end of the hub I2.

The abrasive belt 23 is of the endless type but instead of passing directly about the periphery of the head, it is threaded inwardly between adjacent applicator pad segments toward the hub for passing about the rollers 2|. Thus, the belt Yis greatly increased in length over that of that of the usual type by causing it to alternately pass inwardly and outwardly about the rollers 2| and vthe adjacent applicator pads Il, respectively.

Whereas the immediate application of the wheel to the work presents only the exposed por'- tion of the belt extending over the exterior of the applicator pads, said belt will be caused to creep thereabout and thereby slowly but continuously present fresh, unused abrasive surfaces. This is brought about by the reciprocable action of the applicator pad segments on their guide pins resulting from the intermittent action of centrifugal force when free of the work and retraction when engaging the work. Such reciprocation periodically loosens the belt relative to the surface of the pad upon contact with the work, permitting it to slip relative to the surface of the pad under the influence of friction between tlie applied portion of vthe belt and the surface of the work. This'is followed bya'tightening of the engagement or contact between the pad and the belt as it leaves .the work following the slight frictional displacement. This action becomes progressive as the respective pads come into engagement with and leave the work, yresulting in the automatic feeding of the elon- 'gatedbelt to constantly bring an unused portion thereof into work engaging position.

In the modified form shown inFigs. 3 and 4 the above arrangement is varied to permit of its use in a head of Vsubstantially less diameter. In this form the side plate III] is welded to the hub II2 and a reinforcing outer disk II3, the

Aguide pins I5 and I6 being rigidly secured withinthe side plate IIO. The side plate III is removably mounted relative to said pins, being secured on the radius of the hub -II2, by the threaded nut |22. liach'bearing pin 26 carrying its roller 2i is secured to the-side plate H0 and removably supported at its opposite end bythe plate III. The applicator pad segments I'I are each similarly providedwith a loopedguide strap VI9 embracing and slidably mounted upon the 'guidepins I5 kand I6. The abrasive belt 23 alternately passes 'inwardly about the rollers JZI and outwardly about the adjacent Vapplicator pad segments I'I.

This modiedform isin allrespects the same as above described and functions 'in `the same manner lto bring about the same results, other than to encompass 'the structure 'in `a head of minimum diameter, the rollers 2'I are offset 'to one side of their respective adjacent'applicator Vpad segments so that the loop ofthe belt extending thereabout is directed Aata `substantialangle to'the'radius.

From 'the foregoing it will "be observed that such a. head having vspaced radially slida'ble applicator `pad segments with the 'abrasive belt looped inwardly therebetween to adjacent the hub will provide a more ecientsand'er head of longer life due to the substantially 'increased length of the belt and the creeping or `feeding action to present a fresh unused "surfacethereof during its application to the work.

The invention claimed is:

1. A sander head comprising ahuband 'spaced `side supports, an annular series of applicator segments mounted in'spaced relation about the periphery of said supports for individual and restricted radial slidingmovement, a corresponding annular series of vrollers'carried by said supports inwardly of said segments toward 'said'hub, and an endless abrasive belt passing alternately about 'corresponding rollers and segments respectively 'movable thereover to present an annnular series Vof individual separated abrasive surfaces.

2. A sander head comprising a 'hub and spaced side supports, an annular series of applicator segments defining the periphery of said head, bearing members secured between said side supports slidably mounting said segments thereon for individual limited radial movement, a corresponding annular series of rollers carried by said supports inwardly of said segments towards said hub, and an endless abrasive belt passing alternately about corresponding .rollers and segments respectively movable thereover to present an annular series of individual separated abrasive surfaces.

3. A sander head adapted to be applied to a work surface, comprising a hub, a radially extending frame mounted on said hub, an annular series of applicator segments dening the periphery of said head, means for supporting said segments within said frame for limited radial movement relative thereto and to each other, a corresponding annular series of rollers carried within said frame inwardly of said segments towards said hub, and an endless abrasive vbelt passing alternately about said corresponding rollers and segments respectively movable thereover under the influence of periodic radial movement of said segments and frictional force during application to the work surface.

4. A sander head adapted to be applied `to a work surface, comprising a hub, a radially extending frame mounted on said hub, an annular .series of applicator segments vdening the periphery of said head, means .for supporting said segments in peripherally spaced relation within said frame for limited radial `movement. relative thereto and to each other, a corresponding annular series of anchor members carried within said frame inwardly of said segments toward said hub, and an endless abrasive belt passing alternately about said corresponding anchor members and segments respectively to present an annular series of individually separated abrasive surfaces.

5'. A sander head adapted to be applied to a work surface, comprising a hub, a radially `extending frame mounted on said hub, an annular series of applicator segments .dening the periphery of said head, means for individually and independently supporting said segments in spaced relation within said frame for limited vradial movement relative thereto and to each other, a corresponding annular .series of anchor members carried within said 'frame inwardly of .said segments toward said hub, each of said .anchor members being angularly displaced .in

offset relation to a .radial plane extending between the spaced segments, and an .endless abrasive belt passing alternately about said :corresponding anchor members and segments respectively to provide an inner looped portion directed at a substantial angleto said radial plane.

GEORGE W. BRUNER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,983,361 yPearson Jan. l5, 1935 2,120,624 Pearson June 14, 1938 2,147,901 Hubbard Feb. 21,1939 2,167,573 Jones July 25, 1939 2,206,355 Hubbard July 2, 1940 2,257,061 Morris Sept. 23, 1941 2,401,536 Vonnegut Nov. 5, 1946 

